On vehicles with a manual transmission, worn shift bushings can cause the transmission to pop out of gear, especially when coasting down in 1st or 2nd gear. Replacing all the shift linkage bushings is pretty straight forward and not expensive and will commonly correct this concern.Google+
Car Problem Reports
Toyota Tacoma Worn Shift Bushings Will Cause Manual Transmission to Pop Out of Gear
Toyota Tacoma Problem
Drive Train Affected: 2WD
Visitor, 1998 Toyota Tacoma, 2WD, 140,000 mi
I bought my 98 Tacoma SR% at 132,000 miles and I now have 151,200 miles. At around 140,000 miles when shifting into first gear and barely accelerating the transmission jumps out of gear. This doesn't happen often but often enough to keep me conscientious about being extra sure first gear is fully engaged. So far it's annoying but not bad enough to get it fixed.